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Network Working Group                                           J. Snell
Internet-Draft                                          December 6, 2005
Expires: June 9, 2006


                          Atom Link No Follow
                draft-snell-atompub-feed-nofollow-04.txt

Status of this Memo

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   This Internet-Draft will expire on June 9, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   This memo presents a mechanism that allows feed publishers to express
   preferences over how a consumer processes Atom links and Content-By-
   Reference.









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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . . . 3
   3.  The 'x:follow' extension attribute  . . . . . . . . . . . . . . 4
   4.  The 'x:index' extension attribute . . . . . . . . . . . . . . . 4
   5.  The 'x:archive' extension attribute . . . . . . . . . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . . . 6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 7
   Intellectual Property and Copyright Statements  . . . . . . . . . . 8






































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1.  Introduction

   This docoument specifies a mechanism by which feed publishers MAY
   express how applications consuming Atom documents should handle links
   and referenced content.  For example, a publisher may include an
   enclosure link within a feed but may not wish for applications to
   automatically download the enclosed file when it processes the feed;
   or, the publisher may not wish to allow applications to archive or
   index the enclosure in any way.  The 'follow', 'index' and 'archive'
   attributes introduced herein provide the means for publishers to
   express these preferences.
     noFollowAttributes = {
       attribute follow { "yes" | "no" }?,
       attribute index { "yes" | "no" }?,
       attribute archive { "yes" | "no" }?
     }

   Section 6.3 of the Atom Format specification indicates that Atom
   processors that encounter unknown extensions MUST ignore those
   extensions without altering their behavior.  Because of this
   requirement, there can be no assumption that a particular software
   implementation will support the extensions defined herein.


2.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in BCP 14, [RFC2119], as
   scoped to those conformance targets.

   In this specification, "entry" refers to an atom:entry element.

   In this specification, "feed" refers to an Atom Feed Document.

   In this specification, "head section" refers to the children of a
   feed's document-wide metadata container; e.g., the child elements of
   the atom:feed element in an Atom Feed Document.

   In this specification, the term "extension attribute" refers to a
   namespace qualified element attribute.

   In this specification, the term "link" refers to an atom:link
   element.

   In this specification, the term "referenced content" refers to an
   atom:content element that contains a @src attribute.




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   This specification uses XML Namespaces [W3C.REC-xml-names-19990114]
   to uniquely identify XML element and attribute names.  It uses the
   following namespace prefix for the indicated namespace URI;

   {Ed.  Note: The Namespace must be changed before publication to
   reflect a proper IETF namespace scheme}
     "x": "http://purl.org/atompub/nofollow/1.0"

   This specification uses terms from the XML Infoset [W3C.REC-xml-
   infoset-20040204].  However, this specification uses a shorthand; the
   phrase "Information Item" is omitted when naming Element Information
   Items.  Therefore, when this specification uses the term "element,"
   it is referring to an Element Information Item in Infoset terms.


3.  The 'x:follow' extension attribute

   The 'x:follow" attribute indicates whether applications should
   automatically attempt to follow links and referenced content (e.g.,
   whether or not enclosure links should be automatically downloaded,
   etc).  The value of the attribute is either "yes" or "no".  If
   missing, the value is considered to be indeterminate.  A value of
   "no" indicates that applications SHOULD NOT attempt to automatically
   resolve the referenced resource -- rather, the application should
   wait until a user explicitly requests the linked resource to be
   resolved.

   For example,
     <entry xmlns="http://www.w3.org/2005/Atom"
            xmlns:x="http://purl.org/atompub/nofollow/1.0">
       <id>...</id>
       <title>...</title>
       <link rel="enclosure"
             href="http://example.com/mediafiles/mysong.mp3"
             x:follow="no" />
       ...
     </entry>

   The 'x:follow' attribute MAY be contained by atom:link elements and
   atom:content elements that contain a 'src' attribute.


4.  The 'x:index' extension attribute

   The 'x:index' attribute indicates whether applications should index
   links and referenced content.  The value of the attribute is either
   "yes" or "no".  If missing, the value is considered to be
   indeterminate.  A value of "no" indicates that applications SHOULD



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   NOT index the referenced resource.

   For the sake of this specification, 'indexing' refers to the practice
   of parsing and processing the content of a resource for the purpose
   of populating a database used for searching and other forms of
   analysis.  The intended purpose of using x:index="no" would be for
   the publisher to indicate their preference that the associated
   resource not be processed for searching or analysis purposes.
     <entry xmlns="http://www.w3.org/2005/Atom"
            xmlns:x="http://purl.org/atompub/nofollow/1.0">
       <id>...</id>
       <title>...</title>
       <link rel="enclosure"
             href="http://example.com/mediafiles/mysong.mp3"
             x:index="no" />
       ...
     </entry>

   The 'x:index' attribute MAY be contained by atom:link elements and
   atom:content elements containing a 'src' attribute.


5.  The 'x:archive' extension attribute

   The 'x:archive' attribute indicates whether applications should
   archive the targets of links and content references.  The value of
   the attribute is either "yes" or "no".  If missing, the value is
   considered to be "yes".  A value of "no" indicate that applications
   SHOULD NOT archive the referenced resource.

   For the sake of this specification, 'archiving' refers to the
   practice of maintain a local copy of a resource as part of a
   historical record.  This is different than the practice of
   maintaining locally cached copies of a resource for the sake of
   improving transmission performance and reducing network bandwidth.
   The intended purpose of using x:archive="no" would be for a publisher
   to indicate their preference that local copies of the asociated
   resource not be maintained for archival/historical purposes.
     <entry xmlns="http://www.w3.org/2005/Atom"
            xmlns:x="http://purl.org/atompub/nofollow/1.0">
       <id>...</id>
       <title>...</title>
       <link rel="enclosure"
             href="http://example.com/mediafiles/mysong.mp3"
             x:archive="no" />
       ...
     </entry>




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   The 'x:archive' attribute MAY be contained by atom:link elements and
   atom:content elements containing a 'src' attribute.


6.  Security Considerations

   There are no security considerations introduced by this
   specification.


7.  IANA Considerations

   There are no IANA considerations introduced by this specification.

8.  References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4287]  Nottingham, M. and R. Sayre, "The Atom Syndication
              Format", RFC 4287, December 2005.

   [W3C.REC-xml-infoset-20040204]
              Tobin, R. and J. Cowan, "XML Information Set (Second
              Edition)", W3C REC REC-xml-infoset-20040204,
              February 2004.

   [W3C.REC-xml-names-19990114]
              Hollander, D., Bray, T., and A. Layman, "Namespaces in
              XML", W3C REC REC-xml-names-19990114, January 1999.

   [W3C.REC-xmlschema-2-20041028]
              Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes
              Second Edition", W3C REC REC-xmlschema-2-20041028,
              October 2004.


Appendix A.  Acknowledgements

   The author gratefully acknowledges the feedback from the members of
   the Atom Publishing Format and Protocol working group during the
   development of this specification.









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Author's Address

   James M Snell


   Phone:
   Email: jasnell@gmail.com
   URI:   http://snellspace.com











































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   Internet Society.




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